In my experience people who do this are usually very lonely . They can be living alone, with no-one to talk to on a daily basis.
The other type who are guilty of it are the elderly who have health issues that take up their time and interest and make interacting with others harder than it formerly was.
How many of you have ever told these "friends" how self-centered their behaviour is, and how annoying or hurtful you find it?
Not many, I would think, I am sure you are all too polite to have done so. However, I was, once I had swallowed my hurt pride, grateful to a friend who many years ago told me I talked about myself in company without asking others anything about their lives.
I hope and believe that since that hint, I have remembered to ask others how they are and really listen to their replies, Perhaps we should be less hesitant to remind the "me - me- me" group that conversation is a two way street.